Since pretty much everyone that commented so far seems to like the per route releases better, I felt that I had to come out of the shadows where I usually lurk to share a differing opinion. I actually quite dislike the release of games by route (Mystic Destinies, Tailor Tales, most mobile otomes) or chapter (When The Night Comes, Errant Kingdom, Andromeda Six, Our Life: Beginnings and Always).
That doesn't mean that I don't love those games, in fact I've played and loved all those games that I just listed (including quite a lot of mobile otomes back in the day), it's just that I much prefer to wait until the whole game is done so I can binge-play it all once rather than get a little at a time and then suffer waiting for the next bit. I'm quite impatient in that once I start something, I just want to finish it right away. I'd much rather be patient and wait for the finished product before starting it.
It's also hard to remember the story when it's released in parts, usually months later, and makes me usually have to replay everything I'd already done when the next part comes out, which I could avoid having to do if it just came out all at once. In fact, I sometimes just decide to wait until the whole game is done to play anyway, even if I could have started reading parts of it early, which bums me out even more because then I know that it's self-imposed waiting rather than waiting that's out of my control.
Another point against the per route release method is something you brought up, in that once they release a part, they can't go back to change anything or improve or polish anything, since it's already released. As someone who does some writing of my own, I literally don't understand how someone can release part of an unfinished story knowing that they can't go back and change or improve anything, depending on how the story's going, either plot-wise or quality-of-writing-wise.
And another thing tangentially related to my last point, I think it might actually take longer to release a game this way. Like, I gotta wait even longer because they're releasing it in parts, meaning each release has to be up to standard. They gotta go through the "is this ready for release" testing phase (proofreading, bug testing, quality check, etc) every time they release a new part, instead of just focusing on writing/programming and finishing up the game before going through the "is this ready for release" testing phase once at the end. And if the quality of the writing/game increased toward the later parts or you kinda want to change some parts of the story later, oh well, you can't, since those parts of the game have already been released. I feel like it kinda almost limits what you can do with it.
Ok, I guess I can leave it there. Seems that I'm incapable of typing anything other than a hella long message, sorry. >.< I guess that I've just been noticing that this is more of a trend now with this genre of games, and I've just had a lot of iffy feelings about it. Despite all that, I want you to know that even if you decide to start releasing games in parts like everyone else seems to be starting to do, I will still love your games and play them anyway (just like I've loved and played those games I listed earlier even though they all released in parts). My dislike of that method of release won't be enough to keep me away, don't worry. :) <3